The goals for the NRSA fellowship are to expand the applicant's knowledge and research experience in substance use, psychosocial correlates of substance use, neuropsychology, and advanced statistical methods. The applicant's career goal is to become an independent researcher examining the neurocognitive and affective sequel of substance use during adolescence. Structured training and mentoring experiences are proposed, as well as a carefully aligned research project to examine how clinical and developmental risk factors contribute to concurrent nicotine, cannabis, and alcohol use during adolescence/young adulthood, and in turn impact neurocognitive and affective functioning and psychosocial outcomes. The training plan includes course work, experience with longitudinal methods and data analyses, regular sponsor meetings, clinical practice, and professional development activities. Substance use often is initiated in adolescence, an important period of neurodevelopment and psychosocial development. Concurrent use of nicotine, alcohol, and cannabis is common among adolescents, and this concurrent use may have a catalytic, potentiating effect, escalating dependence and leading to poorer neurocognitive, affective, and psychosocial outcomes. However, few studies have examined the risk factors for concurrent use, along with the neurocognitive and psychosocial outcomes of concurrent substance use during adolescence/young adulthood. The specific aims of the study are to examine: 1) clinical and developmental risk factors that differentiate 4 concurrent substance use trajectory (none, low, medium, and high) groups (a) at baseline and how these factors (b) vary over time, 2) the neurobiological association of frequency of substance use during adolescence on later affective, reward, and other neurocognitive functions in a stratified sample based upon substance trajectories and gender, and 3) whether substance use trajectories mediate the relationship between baseline differences and subsequent neurocognitive and psychosocial outcomes. This study will leverage a well-characterized, longitudinal sample of adolescents transitioning into adulthood, taking advantage of the extensive longitudinal data on substance use and psychosocial variables and proposing additional measures to address new questions as part of the ongoing data collection. Eighty individuals from the parent project will be equally selected from the trajectories to study neurocognitive and affective functioning and psychosocial outcomes. Mentorship will be provided by experts in the areas of substance use, psychosocial correlates of substance use, neuropsychology, and longitudinal methodology and data analysis. The proposed study will be one of the first to integrate psychosocial and neurocognitive correlates of nicotine, cannabis, and alcohol use during adolescence/young adulthood. In addition to enhancing the applicant's skills, the project also has the potential to greatly advance our understanding of risk factors for and the neurocognitive and psychosocial outcomes of concurrent adolescent substance use, a goal consistent with several facets of NIDA's strategic plan.